Energy efficiency and environmental impact have become areas of great concern for society. Thus, many cities have adopted “Dark Skies” initiatives that aim to reduce light pollution by encouraging reduced amounts of light in the nocturnal environment. These initiatives encourage using less light in general, using controls (such as on-off capabilities and time-of-night sensors), and using reflectors and shields to reduce nocturnal light. Such measures may result in energy savings resulting in economic benefits, better nighttime ambience and quality of life, conservation of nocturnal wildlife and ecosystems, and increased visibility at night by reducing glare. One organization that supports such initiatives is the International Dark Sky Association.
In keeping with these initiatives, commercial entities and concerned individuals continue to look for ways to reduce their energy consumption and the amount of light that is emitted upward into the sky. Many individuals are looking to replace old light fixtures with newer fixtures or at least to modify existing light fixtures to be more efficient. The concern is generally found in light fixtures that are employed in outdoor settings, such as street or post top fixtures, but is equally applicable to indoor light fixtures.
An existing post top fixture 10 is shown in FIG. 1. This post top fixture 10 uses a mixture of indirect and direct lighting, and is not necessarily compliant with Dark Skies initiatives. Nor is it very thermally or energy efficient. The post top fixture 10 has a carriage 20 defined by side arms 24 and clear, diffuse or prismatic glass or plastic panes 26 positioned between the side arms 24. There is a hood 16 affixed to the top of the carriage 20. The hood 16 has a cavity 14 that is dimensioned to receive a light source 12. The light sources 12 in such traditional post top fixtures 10 are typically compact fluorescent, high intensity discharge or incandescent light bulbs. In use, it is generally intended for the light to be emitted downwardly from the hood 16, in the area around the pole of the fixture 10. This area is called the “intended area” for the emitted light.
Some of the light is emitted towards the intended areas, resulting in direct lighting of the intended area. The direct light must pass through the panes 26 that define the carriage 20. When light passes through the panes 26, it can result in a loss of optical efficiency of around 8%. The tilted panes 26 may also refract light upwards into the sky. If the panes 26 are dirty then optical efficiency and upward refraction and reflection are even more problematic. Additionally, the panes 26 if constructed of glass or brittle plastic are subject to vandalism by people breaking the panes 26. The panes 26 thus result in inefficiency and might create dangerous conditions.
Additionally, some of the light in traditional post top fixtures 10 is emitted upwardly, which wastes energy and violates Dark Skies initiatives. Thus, a reflector 18 may be placed around the cavity 14 and on the underside of the hood 16 to redirect some of the upwardly emitted light back downward into the intended area, thus resulting in indirect lighting of the intended area. While the reflector 18 does tend to minimize the amount of emitted light that is directed upward, it does not eliminate it entirely as a portion of the refracted light traveling through the panes 26 will be redirected upwards.
Commercial entities and concerned individuals may desire to replace these existing post top fixtures 10 with new light fixtures that are more efficient and are in keeping with Dark Skies initiatives. But the cost of completely replacing existing post top fixtures 10 might be prohibitive, and results in landfill waste. Thus, it may be desirable to modify existing post top fixtures 10 to be more efficient and Dark Skies friendly.
Therefore, there is a need for an efficient light fixture that maximizes the amount of direct lighting supplied to an intended area.
There is also a need for a light fixture that minimizes the amount of upwardly directed light, thus minimizing energy loss and light pollution.
There is also a need to modify existing light fixtures to be more efficient and Dark Skies friendly, rather than replacing the existing light fixtures with new light fixtures.